The preparation of methanedisulfonic acid has been known since at least the turn of the century, but the various methods reported in the literature have serious deficiencies which make the prior methods uneconomical or impractical. Initially, MDSA was prepared by reacting acetylene with fuming sulfuric acid to yield acetaldehydedisulfonic acid (O.dbd.CH--CH(SO.sub.3 H).sub.2) as an intermediate product which was then decomposed to give methionic acid and other by-products; W. Muthmann, Ber. d. deutsch. chem. Ges., 31;1880 (1898); G. Schroeter, Ber. d. deutsch. chem. Ges., 31;2189-90 (1898) and 38;3389-3393 (1905), Annalen der Chemie. 303;114-132 (1898) and 418;161-257 (1919). This method has the disadvantage of requiring the handling of acetylene in dilute form. Acetylene is known to be explosive in concentrated form and is extremely reactive. It cannot be shipped long distances, and for large-scale operations must be used near its point of manufacture.
In 1929 it was reported that the acetylene method had been repeated and produced a poor yield of product, H. J. Backer, Rec. Trav. Chem.. 48;949-52 (1929). Backer also reported in the same reference that he obtained MDSA by heating methylene dichloride with potassium sulfite dissolved in water in an autoclave at 150-160 degrees Centigrade for two hours. The potassium salt is converted to the barium salt and the free acid obtained from it using sulfuric acid. This procedure has the disadvantage of requiring an autoclave and the additional steps involving salts which must be converted to the free acid.
In 1950 J. C. Snyder and A. V. Grosse disclosed in U.S. Pat. No. 2,493,038 a method (example IV) in which methane was autoclaved with sulfur trioxide at 840 psi and 260 degrees Centigrade for 1.5 hours using mercuric sulfate as a catalyst to give a mixture of methanesulfonic acid, MDSA and methanol (present as the ester). This method has the disadvantages of requiring high temperatures and pressures along with the difficult to handle sulfur trioxide and methane gases.
In 1958 J. A. Crowder and E. E. Gilbert disclosed in U.S. Pat. No. 2,842,589 that MDSA could be prepared by reacting methanesulfonic acid with sulfur trioxide, but repetition of this method in our laboratory yielded MDSA contaminated by many by-products. As with the method of Snyder et al, this method has the disadvantage of requiring the handling of sulfur trioxide, which is difficult due to its narrow liquid temperature range (boiling point 44.8 degrees Centigrade and freezing point 17 degrees Centigrade). In addition, trace amounts of water or sulfuric acid act as polymerization catalysts for liquid sulfur trioxide, producing polymers having elevated melting points.
In view of the serious deficiencies of the prior art methods described above, it would be desirable to have a simple method for producing methanedisulfonic acid and other alkanedisulfonic acids in sufficient yields to be economically viable.